Intraspecific facial bite marks in tyrannosaurids provide insight into sexual maturity and evolution of bird-like intersexual display

Paleobiology, Journal Year: 2021, Volume and Issue: 48(1), P. 12 - 43

Published: Sept. 6, 2021

Abstract Intraspecific aggression, or agonism, is a widespread intrasexual selective behavior important to understanding animal behavioral ecology and reproductive systems. Such can be studied either by direct observation inferred from wound/scar frequency in extant species but difficult document extinct taxa, limiting of its evolution. Among archosaurs, crocodylians display extensive whereas birds show extreme visual/vocal intersexual display. The evolutionary origin this divergence, pattern non-avian dinosaurs, unknown. Here we the morphology, frequency, ontogeny intraspecific facial bite lesions (324 lesions) large sample tyrannosaurids (202 specimens, 528 elements) infer patterns aggression theropods. Facial scars are consistent position orientation across tyrannosaurid species, suggesting bites were inflicted due repeated/postured behavior. absent young tyrannosaurids, first appear immature animals (~50% adult skull length), present ~60% adult-sized aggressor:victim size isometry. ontogenetic distribution suggests agonistic associated with onset sexual maturity, scar presence approximately half specimens may relate pattern. Considered phylogenetic context, marks widely distributed fossil crocodyliforms non-maniraptoriform theropods, potential plesiomorphic archosaurs. Their absence maniraptoriform including birds, reflect transition boney cranial ornamentation crocodylian-like avian-like evolution pennaceous feathers.

Language: Английский

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Osteohistology of a Triassic dinosaur population reveals highly variable growth trajectories typified early dinosaur ontogeny

Scientific Reports, Journal Year: 2022, Volume and Issue: 12(1)

Published: Oct. 15, 2022

Abstract Intraspecific variation in growth trajectories provides a fundamental source of upon which natural selection acts. Recent work hints that early dinosaurs possessed elevated levels such compared to other archosaurs, but comprehensive data uniting body size, bone histology, and morphological from stratigraphically constrained dinosaur population are needed test this hypothesis. The Triassic theropod Coelophysis bauri , known bonebed preserving single coeval individuals, an exceptional system assess whether highly variable patterns were present near the origin Dinosauria. Twenty-four histologically sampled individuals less than year at least four years old confirm right-skewed age distribution assemblage. Poor correlations among age, maturity strongly support presence unique, relative archosaurs their living kin.

Language: Английский

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Two braincases of Daspletosaurus (Theropoda: Tyrannosauridae): anatomy and comparison¹

Canadian Journal of Earth Sciences, Journal Year: 2021, Volume and Issue: 58(9), P. 885 - 910

Published: Aug. 19, 2021

For sheer complexity, braincases are generally considered anatomically conservative. However, recent research on the of tyrannosaurids have revealed extensive morphological variations. This line inquiry has its root in Dale Russell’s review which he established Daspletosaurus torosus — a large tyrannosaurine from Campanian southern Alberta. In wake systematic revisions to tyrannosaurines previously assigned Daspletosaurus, one potentially distinct species remains undescribed. paper describes and compares braincase referable this with that holotype for using computerized-tomography-based reconstructions. The two numerous differences externally internally. specimen sp. bottlenecked olfactory tract, short vertical lagena, developed ascending column anterior tympanic recess. many unusual traits, including an anteriorly positioned trochlear root, elongate common carotid canal, chamber basisphenoid recess, asymmetry internal basipterygoid aperture, laterally reduced but medially expanded subcondylar comparison also identified characters unite deep midbrain flexures endocasts. character variations known other correlate body size maturity, or represent individual Therefore, taxonomic phylogenetic signals can be isolated background more comprehensive approach by additional specimens. New information is consistent emerging view tyrannosaurid as highly variable, ontogenetically dynamic complexes.

Language: Английский

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Paranasal sinus system and upper respiratory tract evolution in Mesozoic pelagic crocodylomorphs

The Anatomical Record, Journal Year: 2021, Volume and Issue: 305(10), P. 2583 - 2603

Published: Aug. 16, 2021

Abstract Thalattosuchians were a predominately marine clade of Mesozoic crocodylomorphs, including semi‐aquatic teleosauroid and obligately pelagic metriorhynchid subclades. Recent advances in our understanding thalattosuchian endocranial anatomy have revealed new details the evolutionary transition from terrestrial to taxa. Paranasal sinuses, however, received little attention. Herein, we investigate evolution paranasal sinus system part upper respiratory (nasopharyngeal ducts) Thalattosuchia, by reconstructing nasal CT scans seven skulls: one teleosauroid, two basal metriorhynchoids four metriorhynchids. Our outgroups were: three extant crocodylian species (including adult subadult skulls) crocodyliform Protosuchus . We found thalattosuchians exhibit exceptionally reduced systems, solely comprising antorbital sinus, as has been previously proposed. The Palgiopthalmosuchus gracilirostris Pelagosaurus typus both an partially located medial external fenestra broadly communicating with dorsal alveolar canal. In metriorhynchids, cavity is more extensive than taxa possibly had active function associated hypothesized accessory suborbital diverticulum, but reconstructions are insufficient confirm or reject presence such diverticulum. nasopharyngeal ducts metriorhynchids dorsoventrally enlarged, enabling stronger ventilation. sequence acquisition craniofacial adaptations show mosaic pattern appears predate many skeletal adaptations, suggesting these changes occurred early transition.

Language: Английский

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How smart wasT. rex? Testing claims of exceptional cognition in dinosaurs and the application of neuron count estimates in palaeontological research

bioRxiv (Cold Spring Harbor Laboratory), Journal Year: 2024, Volume and Issue: unknown

Published: Jan. 12, 2024

Recent years have seen increasing scientific interest in whether neuron counts can act as correlates of diverse biological phenomena. Lately, Herculano-Houzel (2023) argued that fossil endocasts and comparative neurological data from extant sauropsids allow to reconstruct telencephalic Mesozoic dinosaurs pterosaurs, which might proxies for behaviors life history traits these animals. According this analysis, large theropods such Tyrannosaurus rex were long-lived, exceptionally intelligent animals equipped with 'macaque- or baboon-like cognition' whereas sauropods well most ornithischian would displayed significantly smaller brains an ectothermic physiology. Besides challenging established views on dinosaur biology, claims raise questions count estimates could benefit research general. Here, we address findings by revisiting Herculano-Houzel's work, identifying several crucial shortcomings regarding analysis interpretation. We present revised encephalization dinosaurs, derive phylogenetically informed modeling amended dataset endocranial measurements. For large-bodied particular, recover lower than previously proposed. Furthermore, review the suitability variables numbers relative brain size predict cognitive complexity, metabolic rate coming conclusion they are flawed Instead relying when reconstructing argue integrative studies needed approach complex subject.

Language: Английский

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